St. Mary's County, MD Water Table Trend
Is the water table dropping in St. Mary's County, MD?
St. Mary's County's representative monitoring well shows depth to water declining faster than most declining counties, a fitted trend of 15.2 ft per decade over 82 years of readings.
This is one representative well, not a county-wide survey, the same grain limit every page here discloses.
St. Mary's County's source well, in detail
Depth to water at the last reading was 183.8 ft below land surface. Readings span 1943-06-25 to 2025-09-09, 50 measurements from USGS well USGS-381715076261601 (Sm Df 10), part of the National Water Information System. The qualifying bar and the OLS fit behind this trend are documented in the methodology guide.
How St. Mary's County compares nationally
St. Mary's County sits at rank 1423rd of 1,449 ranked counties, ordered rising-to-declining, so a low number means a rising water table and a high one means fast decline. St. Mary's County, Maryland is home to about 116,469 people. See the fastest-moving counties guide for how St. Mary's County stacks up against the most extreme cases nationally.
If you own a well in St. Mary's County
A dropping water table means a residential pump has to reach deeper and work harder, which shortens its life. In St. Mary's County, that trend is real, not assumed: 15.2 ft per decade over 82 years.
Depth and quality are separate questions
This page answers a depth question, not a quality one. A well in St. Mary's County can be stable in depth and still worth testing for quality, or declining and still test clean, the two are measured separately, and only a direct test settles the second one.